Heretofore, as a sheet conveyance apparatus, there has been extensively known one which includes a paper feed cassette for placing sheets of paper thereon, and rollers for conveying the sheets of paper one by one (See JP-A-2001-206566.).
This device includes in addition to the above configuration, a sheet end sensing sensor which is constructed of a photosensor and an actuator in order to determine the timing (conveyance interval) of the sheet conveyance, and a sensing switch which is disposed in order to detect the presence or absence of the paper feed cassette.
With the above configuration, each of the conveyance of the sheet and the presence or absence of the paper feed cassette is detected by the dedicated detection means. Since the number of components enlarges in such a configuration, the assemblage of the components becomes complicated to the corresponding extent, and curtailment in the cost and reduction in the size of the device are hampered.
Incidentally, an image formation apparatus is formed with an opening in the side surface of an apparatus body case, and it accommodates a paper feed cassette in which sheets of paper are stacked, in a manner to be capable of pulling out the paper feed cassette through the opening. In an image formation operation, the sheets of paper in the paper feed cassette are fed to a sheet conveyance path one by one by means of a paper feed roller inside the apparatus body case, and the sheet is formed with an image by an image formation section and is ejected into a paper ejection tray through a fixation unit while being conveyed by conveyance rollers.
Meanwhile, in the image formation apparatus of this type, a gap needs to be provided between the opening of the apparatus body case and the paper feed cassette for the purpose of attaining the smooth attachment/detachment of the paper feed cassette. Accordingly, noise made when the sheet being conveyed rubs in the sheet conveyance path or when it rubs with the various rollers, noise made when the sheets of paper are frictionally separated one by one, and the like noise (hereinbelow, termed “rustlings”) are prone to come out from the gap.
Besides, some image formation apparatuses employ a so-called “letter-S path scheme” wherein, as disclosed in JP-A-2004-157463 below, the sheet is reversely conveyed so as to be folded back, near that front side of the apparatus on which the attachment/detachment manipulation of the paper feed cassette is performed. The scheme has the problem that especially the rustlings in the reversal conveyance are prone to come out from the gap between the opening and the paper feed cassette.
Here, in order to suppress the rustlings, there is thought out a method wherein an elastic member of sponge or the like is stuck to the apparatus body case or the paper feed cassette at either of parts which vertically oppose to each other through the gap between the opening of the apparatus body case and the paper feed cassette, thereby to cover the gap. The gap, however, is provided in order to smoothen the attachment/detachment of the paper feed cassette. When the gap is shut up by the sponge so as to be vertically covered, there can occur the problems that the elastic member is strongly rubbed every operation of attaching or detaching the paper feed cassette, to be torn off or worn away, so a sealability (noise prevention property) degrades, and that the smooth attachment and detachment of the paper feed cassette are impossible.